A family study of primary affective disorders is being performed. Biologic characteristics of the patients are evaluated for usefulness as genetic markers of vulnerability to affective disorders. Among the biologic variables studied in this way are platelet monoamine oxidase activity and erythrocyte catechol-0-methyl transferase activity. Genetic linkage of affective disorders to known chromosomal markers is also studied. Mathematical models of genetic transmission are being developed for application to these data.